Systems and methods for digital processing of satellite communications data

ABSTRACT

A digital payload for processing a sub-band spectrum received on an uplink beam at a communications satellite includes a digital channelizer, a digital switch matrix and a digital combiner. The digital channelizer divides the sub-band spectrum into a plurality of frequency slices that can be routed by the digital switch matrix to any of a number of receiving ports. A digital combiner receives the frequency slices and re-assembles them to form one or more output sub-bands for transmission on an output beam of the communications satellite. The digital payload may also include an embeddable digital regeneration module configured to demodulate some or all of the sub-band spectrum to extract a digital bitstream therefrom. The digital bitstream may be processed to implement code-based multiplexing, switching, access control, and other features.

PRIORITY CLAIM

This application claims priority of U.S. Provisional Application Ser.No. 60/443,517 filed on Jan. 28, 2003. This application also claimspriority of U.S. Provisional Application Ser. No. 60/443,664 filed onJan. 29, 2003. Both of these disclosures are incorporated herein byreference in their entirety.

TECHNICAL FIELD

The present invention generally relates to satellites, and moreparticularly relates to a digital architecture for satellites.

BACKGROUND

Satellites have become invaluable tools in such diverse fields asnavigation, communications, environmental monitoring, weatherforecasting, broadcasting and the like. Hundreds of man-made satellitesnow orbit the earth, and each year many more are launched from variousnations around the world. Moreover, many homes, businesses andgovernment organizations now use satellite systems on a daily basis forentertainment, communications, information gathering and other purposes.

A typical modem satellite has a metal or composite frame that houses apower source (e.g. one or more batteries, solar cells and/or the like)and various electronic components, as well as one or more antennas. Thecomponents generally include one or more “transponders”, which areclusters containing one or more radio receivers, frequency translatorsand transmitters. The total bandwidth of the satellite is provided bythe number of transponders, each of which may have a typical bandwidthof 30-70 MHz or so. One type of commercially-available satellite, forexample, has a total available bandwidth of 3,528 MHz divided acrossforty-five C-band and sixteen Ku-band transponders. These transpondersare collectively referred to as “the payload” of the satellite.

As shown in FIG. 1, a typical analog transponded communications payloadreceives multiple uplink beams from the earth or another satellite viaan uplink antenna. Each of the received beams is amplified with a lownoise amplifier (LNA) and down-converted (D/C) for further processing.The down-converted beams can then be switched, multiplexed (MUX) orotherwise routed and combined prior to upconversion and re-transmissionon a downlink beam to the earth or another satellite.

Although some analog transponded satellites may include limitedswitching and multiplexing functionality, these features are restricted,with switching limited to point-to-point mapping of entire uplinkantenna beams to particular downlink antenna beams. This leads to majorinefficiencies in the use of satellite bandwidth. A satellite customertypically purchases a “transponder”, or dedicated block of bandwidth ona satellite, for a period of one year or more. Transponder bandwidthsare typically fixed in the satellite during design (e.g. at 33, 50, 70MHz, etc.) and are not finely adjustable after the satellite isconstructed. Each transponder provides a connection with dedicatedbandwidth and power between two points on the earth (point-to-point), orbetween one point and broad geographic areas (broadcast). While thisarrangement is relatively flexible with respect to the type of signalscarried, there are major disadvantages in terms of bandwidth efficiencyand transmit power control. Should a satellite customer need slightlymore bandwidth than that provided by the transponder, for example, thesatellite customer must generally purchase another “transponder-sized”bandwidth segment of 33-70 MHz. Further, if a satellite customer doesnot use all of its transponder bandwidth, this excess capacity remainsunused, wasting a limited and valuable commodity. While some customershave attempted to address this inefficiency by sub-allocating purchasedtransponder bandwidth to other end users via dedicated terrestrialterminal equipment and extensive special arrangements, sub-allocationtypically requires the satellite customer to trust the end users tocontrol their own power and bandwidth usage because no positive controlis available to regulate bandwidth and power consumption onboard thesatellite. In addition, satellite “pirates” frequently “piggyback”signals onto unused transponder bandwidth, robbing transmit power anddegrading communication link performance for legitimate users. Due inlarge part to these inefficiencies and other factors, the cost ofsatellite communications remains relatively high compared to terrestrialcommunications systems, thereby limiting the widespread adoption ofsatellite communications for many applications.

Satellite payloads have evolved more recently to take advantage ofdigital technologies for enhanced flexibility and control. Digitalsatellite payloads generally function in either a channelized manner ora regenerative manner. In the former case, a digital payload simulatestraditional fixed analog transponders, but adds the ability to finelydivide, control and monitor bandwidth and power allocation onboard thesatellite. Digital transponded payloads normally have the ability toperform switching of inputs to outputs in a highly flexible manner,enabling them to act as virtual “telephone exchanges”, where a requestfor a channel with specific bandwidth/power and antenna characteristicsis made, the channel is set up, used, then disconnected. This “circuitswitched” capability ensures that only the bandwidth, transmit power andcoverage needed is provided, and only when it is needed. Sincetransponded channels are merely repeated signals, without anymodification, transponder payloads can carry any type of signal withoutregard to format or modulation mode. Unlike transponded payloads,regenerative payloads perform demodulation and remodulation of uplinkedsignals, recovering and processing not just the user signal, but alsothe user data embedded within the signal, enabling the payload to actupon it in a desired manner. Embedded data is most often used forautonomous routing in packet based systems and for security functions,as in many government satellites, or both. In particular, errordetection and correction can be performed on demodulated data before itis retransmitted, thereby allowing regenerative satellite payloads togenerally have better link performance than transponded payloads. Thesecharacteristics and others make regenerative payloads the most efficientavailable in terms of control, bandwidth and power use. Regenerativesystems, however, are commonly built to process a single set of signaland data formats that is fixed at design time. Such systems do nottypically provide universal signal compatibility as may be availablefrom transponded payload possesses.

As satellite payload evolution continues, satellite customers areprogressing from analog transponded to digital transponded to digitalregenerative approaches to extract the maximum revenue bearing bandwidthand power from spectrum allocations fixed by law. Digital transpondersystems may be relatively easily made to be backward compatible withanalog transponder systems since neither system provides onboard dataprocessing. Regenerative systems are generally not backward compatible,however, due to their requirements for specific signal and data types.While the transition from analog transponded payloads to much moreefficient digital transponded payloads is clear, the path to provideeven more efficient regenerative payload capability without droppinglegacy system users or requiring the satellite to carry significantlymore processing electronics has been difficult. To avoid loss ofoperation and to provide continuous revenue flow, existing satellitecustomers generally desire to transition transponded end users toregenerative services in a gradual manner, over the many-year life spanof an expensive satellite asset.

It is therefore desirable to improve the flexibility and functionalityof satellite payloads used in data communications in commercial and/orgovernment settings. It is further desirable to provide a satellitepayload capable of simultaneously mixing transponded and regenerativemodes in a hardware efficient payload, and to provide in-serviceprogrammability for regenerative signal and data formats. Furthermore,other desirable features and characteristics will become apparent fromthe subsequent detailed description and the appended claims, taken inconjunction with the accompanying drawings and this background of theinvention.

BRIEF SUMMARY

According to various exemplary embodiments, both digital transponded anddigital regenerative functions are provided within an all-digitalsatellite payload. By combining transponded and regenerative functionsinto a common digital platform, numerous efficiencies of scale arerealized, and the overall efficiency and functionality of the satelliteis dramatically improved.

In one embodiment, a digital payload for processing a sub-band spectrumreceived on an uplink beam at a communications satellite includes adigital channelizer, a digital switch matrix and a digital combiner. Thedigital channelizer divides the sub-band spectrum into a plurality offrequency slices that can be routed by the digital switch matrix to anyof a number of receiving ports. A digital combiner receives thefrequency slices and re-assembles them to form one or more outputsub-bands for transmission on an output beam of the communicationssatellite. The digital payload may also include an embedded digitalregeneration module configured to demodulate some or all of the sub-bandspectrum to extract a digital bitstream therefrom. The digital bitstreammay be processed before, during and/or after the routing function toimplement code-based switching, multiplexing, access control, outputlinearization and other features.

In another embodiment, a method of processing a sub-band spectrumreceived on an uplink beam at a digital payload for a communicationssatellite suitably includes the steps of digitally dividing the sub-bandspectrum into frequency slices and routing each of the frequency slicesbetween a number of receiving ports. Some or all of the frequency slicesmay be digitally demodulated, processed and/or remodulated before,during and/or after routing, as appropriate. The routed and/or processedfrequency slices are then digitally re-assembled to thereby form outputsub-bands for transmission on one or more output beams of thecommunications satellite.

Other aspects variously relate to satellite components, systems andmethods. The concepts set forth further herein allow new techniques forcommercializing satellite resources, and several new business modelswithin the satellite field. These and other aspects of various exemplaryembodiments are set forth in detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will hereinafter be described in conjunction withthe following drawing figures, wherein like numerals denote likeelements, and

FIG. 1 is a block diagram of an exemplary prior art satellite payload.

FIG. 2 is a block diagram of an exemplary satellite having a flexibletransponder payload;

FIG. 3 is a block diagram of an exemplary digital satellite payload;

FIG. 4 is a perspective view of an exemplary embodiment of a packetprocessing digital payload;

FIG. 5 is a block diagram of an exemplary embodiment of apacket-processing digital payload;

FIG. 6 is a block diagram of an exemplary embodiment of a multi-slicedigital payload;

FIG. 7 is a block diagram of an exemplary satellite having a modulardata handling capability;

FIG. 8 is a block diagram of a satellite having an exemplary all-digitalpayload;

FIG. 9 is a flowchart of an exemplary process for allocating bandwidthin a digital satellite payload;

FIG. 10 is a flowchart of an exemplary process for allocating satelliteresources; and

FIG. 11 is a conceptual diagram of an exemplary digital satelliteimplementation.

DETAILED DESCRIPTION

The following detailed description is exemplary in nature and is notintended to limit the invention or the application and uses of theinvention. Furthermore, there is no intention to be bound by any theorypresented in the preceding background of the invention or the followingdetailed description.

According to various exemplary embodiments, a new digital architectureprovides a backward-compatible, broadband, switched channelizing digitalpayload for communications satellites. Because the amount of usablebandwidth available from a digital payload may be much greater than thatprovided by a corresponding analog payload, the cost of bandwidthprovided by the satellite is suitably reduced, thereby allowing reducedpricing to consumers and/or greater profit margins for bandwidthsuppliers. Moreover, the integrated digital architecture allows foradditional features and functionalities not previously available fromother satellite payloads. As an example, various embodiments allowpayload resources (e.g. bandwidth, power, frequency plans, antennacoverages, etc.) to be readily re-assigned during design ormanufacturing of the satellite, or even on orbit, thereby greatlyimproving the flexibility of satellite designs. By allowing bandwidthand other resources to be adjusted on-orbit, the satellite can adapt tochanging consumer needs, thereby improving risk assessment of satelliteimplementations and enabling new marketing strategies for selling orreselling satellite bandwidth. These new strategies, in turn, providenew revenue streams for bandwidth providers while improving service toconsumers.

The various embodiments of the new architecture result in an all-digitalsatellite payload that is modular, reconfigurable and programmable.Although various embodiments of the new architecture are described usingterms such as “flexible transponder”, “modular data handler” and“flexible satellite”, a wide array of equivalent embodiments may beformed using the general concepts set forth herein.

Turning now to the drawing figures and with reference now to FIG. 2, anexemplary satellite payload 200 suitable for use with satellitecommunications is shown. In the embodiment shown in FIG. 2, payload 200suitably includes any number of input amplifiers 206A-n, optionaldownconverters (D/C) 208A-n, output amplifiers 210A-I, output switches212A-j and output multiplexers 214A-k that are arranged to interoperatewith a digital transponder unit 202 to provide digital processing ofinput beams 204A-n and to create output beams 216A-n that aretransmitted to a receiver at another satellite or at the earth's surfacevia a suitable antenna.

In operation, each input beam 204 is received via a suitable antenna(not shown in FIG. 2, but described more fully below). Each beam may befiltered to isolate an appropriate band of frequencies (i.e. “sub-bands”or “channels”) to be amplified by a low noise amplifier (LNA) or otherinput amplifier 206 to improve the strength of the received signal. Theamplified sub-band is then downconverted from the received frequency toa suitable intermediate frequency (IF) for digital processing. While theembodiment shown in FIG. 2 shows block down-conversions of 250-750 MHzsections of input bandwidth and switching and filtering of 24-72 MHzchannels, any other frequency bands or ranges may be used in a widearray of alternate embodiments. For example, high-qualityanalog-to-digital converters may be used to sample incoming sub-bands atrates as high as 550 MHz or greater, thereby reducing or eliminating theneed to downconvert the amplified sub-bands in many embodiments, asdescribed more fully below. While conventional satellites most commonlyuse C and Ku band receive or transmit frequencies, the techniquesdescribed herein are extendable to UHF, L, S, and Ka band frequencies,as well as any other frequencies.

While conventional circuit switching architectures (e.g. that shown inFIG. 1) simply switched and multiplexed entire channels between inputand output beams, various embodiments of digital transponder unit 202are capable of digitally dividing each sub-band into frequency slicesthat can be separate switched, processed, routed and re-combined inoutput sub-bands as described more fully below. To this end, the digitaltransponder unit 202 replaces the input multiplexers and associatedswitches, cabling, etc. shown in FIG. 1 while providing additionalfunctionality and efficiency not available in prior systems. Thisdigital processing enables a number of new features that were notpreviously available, including reconstruction filtering of individualslices, traffic monitoring, transmit linearization, optimization, accesscontrol and the like. Moreover, the digital transponder 202 allows fortailoring of bandwidth and other resource allocations, thereby greatlyimproving the efficiency of payload 200. Bandwidth allocations on bothuplinks 204 and downlinks 216 can be adjusted in real time duringoperation, for example, to re-assign excess bandwidth to beams orsub-bands experiencing increased traffic demands. Variousimplementations of digital transponder units 202, components andassociated processing techniques are described below in greater detail.

The output sub-bands assembled by digital transponder unit 202 areappropriately amplified with traveling-wave tube amplifiers (TWTA),solid-state power amplifiers (SSPA) or other suitable output amplifiers210. Although the particular output power varies from embodiment toembodiment according to such factors as the altitude above earth,transmit frequencies used, etc., typically output power of about 50 Wmay be used at C band frequencies and about 80-120W of power may be usedat Ku band. The outputs of some or all of the output amplifiers 210 maybe switched, multiplexed together at output muliplexers 214, and thenre-transmitted through the transmit antennas to form output beams 216.Before multiplexing, optional variable power dividers (not shown inFIG. 1) may be used to allocate power to the various coverage areas asappropriate.

FIG. 3 shows one logical layout of an exemplary digital satellite system300. With reference now to FIG. 3, an exemplary digital transponder unit202 suitably communicates with any number of uplink antennas 303A-N andany number of downlink antennas 315A-N to digitally process uplink beams204A-N and downlink beams 216A-N, respectively. As described above,uplink beams 204 may be downconverted in various embodiments to allowsampling and A/D conversion at an appropriate frequency, although thedownconverters 208 may be eliminated or incorporated into transponderunit 202 in various alternate embodiments.

Uplink and downlink antennas 303 and 315 may be implemented with anyconventional antennas used in satellite communications. In variousembodiments, antennas 303 and 315 are implemented with digital or analogbeamforming antennas having any number of independently-addressabletransmit/receive elements. Examples of such antennas include the variousspot beam dishes, multi-beam feed antennas, direct radiating arrayantennas and/or phased array antennas available from Boeing SatelliteSystems of Los Angeles, Calif. and others.

Digital transponder unit 202 suitably provides on-board switching andsub-channel routing functionality. Because signals are digitally routedwithin transponder unit 202, variable sub-channel bandwidth cangenerally be provided with negligible degradation in signal quality.Channel widths, spacing and switching may be further programmed orotherwise modified on orbit, and some or all of the output sub-channelsmay be optionally configured with a commandable downlink level controlas appropriate. Further embodiments may also optimize uplinkconnectivity, as described more fully below (e.g. in conjunction withFIG. 10).

As shown in the exemplary embodiment of FIG. 3, digital transponder unit202 suitably includes a digital channelizer module 302, a digital switchmatrix 304, a digital combiner 306 and a digital regeneration module308. The various modules and sub-systems shown in FIG. 3 are intended aslogical constructs; in practice, each sub-system may be implemented withany combination of physical hardware and/or software components. Eachuplink beam and/or sub-band spectrum, for example, may have one or morecorresponding processing cards or “slices” associated therewith, witheach of the various cards communicating over a common backplane bus.Such an embodiment is described below in conjunction with FIG. 4.Alternatively, the various functions and channel assignments may beshared between various cards, modules or components in a wide array ofalternate embodiments.

Channelizer 302 includes any digital circuitry and/or software modulescapable of receiving a digital representation of the sub-band spectrumreceived on an uplink beam 204 and of dividing the sub-band spectruminto any number of equally or unequally sized frequency ‘slices’ 310.Slices 310 are also referred to herein as “packets” because time or codedivision multiplexed information segments within the slices may bereadily routed independently of the other slices and segments in thesub-band spectrum, as described below. In various embodiments, digitalchannelizer module 302 is implemented with an application specificintegrated circuit (ASIC). Exemplary ASICs formed using complementarymetal oxide semiconductor (CMOS) technologies and the like are availablefrom International Business Machines of Armonk, N.Y. and others.

Switch matrix 304 is any hardware and/or software structures capable ofdirecting frequency slices 310 between various ports 312 as appropriate.In various exemplary embodiments, switch matrix 304 is implemented withone or more switch ASICs associated with each sub-band or processingcard, with each ASIC within matrix 304 being interconnected by a sharedbus or other communications medium as described below. The Various ASICsmay be custom-built integrated circuits, for example, or may befabricated from field programmable gate arrays (FPGAs) that have beensuitably programmed to store and/or forward digital data as appropriatewithin switch matrix 304.

Ports 312 are any hardware or software constructs (e.g. memorylocations, bus addresses, Unix-type socket ports, or other physical orlogical constructs) capable of receiving frequency slices 310 forsubsequent processing. Switch matrix 304 may provide for in-beam and/orcross-beam point-to-point, multi-cast and/or broadcast switching. In theexemplary embodiment shown in FIG. 3, for example, frequency slice 310Ais shown directly mapped to port 312A, which is associated with the samesub-band spectrum 204 as slice 310A. Alternatively, one or more slices310 may be mapped to ports 312 associated with one or more other beams204. FIG. 3 shows slice 310B mapped to ports 312B for an in-beammulti-cast, for example, with slice 310C mapped to multiple ports 312Con different beams to show an example of cross-beam multicasting.Because such switching is performed digitally, little or no signaldegradation typically results.

Regeneration module 308 is any hardware and/or software construct(s)capable of further processing the digital data encoded within thevarious frequency slices 310. In an exemplary embodiment, suchprocessing is executed by one or more fixed ASICs or programmable chips314 embedded within payload 300. Because the frequency slices 310 arealready processed digitally by the channelizer, the various bit streamsencoded within each slice 310 may be economically demodulated, furtherprocessed and remodulated prior to transmission using any appropriatealgorithms or techniques, without major duplication of expensivesampling and filtering functions. This synergy between channelized andregenerative architectures enables both types of processing to shareoverlapping functionality and to coexist, without requiring the totalduplication of circuitry that casual inspection might suggest. Types ofdigital processing that may be performed include access verification,encryption, code division multiplexing (e.g. CDMA), data regeneration(i.e. recovery of corrupt or unclear data), compression, packetswitching and/or any other data processing. Demodulation/remodulationmay take place at any point during the channelizing/routing process, andremodulation need not take place immediately following any processinghandled by regeneration module 308. Demodulated data may be channelizedand/or routed prior to remodulation, for example, or otherwise processedas appropriate. In the exemplary embodiment shown in FIG. 3, forexample, a frequency slice 310E is shown routed to a port associatedwith an optional programmable modulator 314B associated with anotherbeam 204B for processing.

Combiner module 306 is any hardware and/or software constructs capableof re-assembling the various frequency slices into new sub-bands 216.After the frequency slices 310 are routed to the appropriate ports 312and/or otherwise processed as desired, data received at the variousports 312 associated with each downlink beam 216 are suitably combinedprior to re-transmission. The re-combined sub-bands are converted toanalog signals that can be transmitted on a downlink antenna 315 bydigital-to-analog converters (DACs) 316.

In operation, then, digital transponder unit 202 suitably receivessub-band spectra from the various uplink beams 204, divides the sub-bandspectra into frequency slices that can be individually routed across thevarious beams, provides any desired additional processing (e.g. signalreconstruction, encryption, etc.) and recombines the various slices tocreate new downlink beams 216. The overall capability of unit 202 isgreatly enhanced through the additional digital signal and dataprocessing that can be performed on digitized signals and data packets.Further, the effective bandwidth of system 300 is greatly increased incomparison to similar analog circuit-based systems by the efficiencywith which user signals and data can be packed together to fit intoavailable bandwidth with minimum unusable segments. This is becausesignals and data can be processed in relatively small segments ratherthan in fixed-sized end-to-end circuits. The overall efficiency ofsystem 300 in terms of bandwidth, power consumption and other factors isgreatly enhanced, since demands for additional capability on one beam(or portion of a beam) 204 can be met with excess available capacityfrom the same or another beam.

With reference now to FIG. 4, an exemplary hardware implementation of adigital signal processing (DSP) payload 400 suitably includes a cabinet402 housing various processing cards 404, 406 as appropriate. Cabinet402 typically includes any number of slots for receiving the variouscards as well as a backplane bus to facilitate data transfers betweencomponents on separate cards. Cabinet 402 may also have appropriateconnects for providing electric power to each card 404, 406.

Because different embodiments may incorporate any number of processingcards, DSP payload 400 readily scales to implementations of any size bysimply adding or removing processing cards from cabinet 402. Variousimplementations may include, for example, any number of transpondercards 404 as well as one or more resource management cards 406.Redundant (“backup”) cards may also be provided in the event that one ormore cards should fail during operation. In one embodiment, cabinet 402supports three active transponder cards 404 and a resource managementcard 406, as well as a backup transponder card and a backup managementcard.

Each card 404, 406 housed within cabinet 402 suitably interfaces withthe backplane bus for inter-card data communications. Although any busdesign could be used, exemplary embodiments may use industry standardbus architectures such as the peripheral component interface (PCI) bus,VMEbus, or any of the other buses described in various IEEE, ARINC,MIL-STD and/or other commercial and/or military communicationsstandards. In one embodiment, the backplane bus is based upon amatched-impedance UNILINK switch fabric available from InternationalBusiness Machines of Armonk, N.Y.

The various transponder cards 404 operating with payload 400 typicallyinclude one or more inputs capable of supporting one or more inputchannels as well as an interface to the backplane bus, suitableprocessing circuitry, and any number of outputs. In various embodiments,input and output slices with six or more 540 MHz input channels may beprovided, although other embodiments may have any number of channelsoperating at any frequency. Various embodiments may include any numberof input and/or output slices (e.g. 1-7 inputs and 1-7 outputs); thenumber of input slices need not match the number of output slices.Moreover, transponder cards 404 typically include a microcontroller,digital signal processor or other processor as well as a distributeddataswitch and associated circuitry for supplying power to the card.Although any processor could be used with the various embodiments, oneexemplary embodiment uses PowerPC 750 processors on both transpondercards 404 and resource management cards 408. Data processing for switchmatrix 304 (FIG. 3) and other functions may be shared between multiplecards 404, 406 to further improve redundancy and load sharing of system400.

Referring now to FIG. 5, an exemplary DSP payload 500 is shown inlogical form as including any number of channels 501A-n interconnectedby data switch 510. Each channel 501 generally corresponds to onesub-band spectrum received on an uplink beam 204, as appropriate. Anynumber of channels 501 may be processed on a common data processing card404 described above. Payload 500 also includes power supply 518,telemetry and command (T&C) processing 520 and clockgeneration/distribution 522 functions as appropriate. T&C processing 520and/or clock generation 522 functionality may be provided by one or moreresource management cards 406 (FIG. 4), or may be shared between one ormore data processing cards 404.

Each channel 501 suitably includes various modules for digitallyprocessing received signals. In the exemplary embodiment shown in FIG.5, the analog baseband signal received from the uplink antenna is firstfiltered and A/D converted at 502 to produce digital equivalents thatcan be further processed. As mentioned above, filtering and A/Dconversion may be handled within payload 500, or may be handled in aseparate A/D converter that can be located near the antenna to reducesignal noise, interference and other sources of error or distortion. Thedigital baseband signals may be further filtered 504 or otherwiseshaped/processed to obtain a desired digital sub-band spectrum, forexample. These digital signals may be demodulated at demodulation module506 as appropriate. Demodulator 506 suitably operates at variable ratesto accommodate different data types and protocols from varying datasources. The demodulated signals are then decoded, descrambled orotherwise processed 506 to a digital bitstream that can be packetized,routed and/or otherwise processed. Decoding module 508 suitablycommunicates with the T&C module 520, which gathers information aboutthe data and provides any command instructions to process the data asdesired. The demodulated data can be channelized and routed from anyinput port to any output port on payload 400. Switch 510 thereforeaccommodates switching and routing of individual packets and/or circuitsby mapping various slices of decoded packet data to one or more switchoutput ports, as described above in conjunction with FIG. 3.

Additional processing of the decoded data packets may take place before,during or after routing by switch 510. Examples of the various types ofprocessing that may be implemented include encryption/decryption, accesscontrol/authentication, data compression/extraction, protocolconversion, signal regeneration, error correction and the like. Becausethe decoded data packets are simply streams of digital bits, any type ofprocessing can be performed on the data prior to remodulation and D/Aconversion. Such processing may be controlled and/or carried out by T&Cmodule 520 and/or by other processors on any transponder card 404 orresource management cards 406 (FIG. 4).

After digital processing and routing, the various digital packets/slicesare recombined and formatted 512 as appropriate. The recombined packetscan then be encrypted, coded, multiplexed, re-modulated or otherwiseprocessed by module 514 prior to transmission on a downlink beam. DSPpayload 500 may also include filtering and D/A conversion capability516, or D/A conversion may take place in closer physical proximity tothe downlink antennas to reduce noise, distortion and the like.

Additional detail of an exemplary implementation of a digital payload600 having three multi-port DSP processing slices 406A-C is provided inFIG. 6. With reference to FIG. 6, digital payload 600 suitably includesany number of DSP slices 406, each of which include an ADC 604, achannelizer 608, a digital switch fabric 622, a digital combiner 610,and a DAC 612, in addition to an optional regeneration module 616. Eachslice 406 also includes power circuitry 618 for providing electric powerto the various slice components as appropriate. As described above inconjunction with FIG. 3, each of the various data processing componentsmay be implemented with application-specific integrated circuitry, orwith any other combination of hardware and/or software.

As described above, each processing slice 406 receives sub-band spectraor other input signals from an uplink antenna. In FIG. 6, these sub-bandspectra are shown as 560 MHz frequency bands provided in groups of fourbands at an input port 602, although other embodiments may processdifferent numbers of channels and/or channels of varying bandwidths.Each of the input signals are received at slice 406, where the signalsare converted to digital equivalents by ADC 604. These digitalequivalents may be provided in any manner to a channelizer circuit 608.In the embodiment shown in FIG. 6, digital equivalents are provided via8-bit parallel data connections, although alternate embodiments may useany level of bit resolution transmitted over any serial and/or parallelconnection. The channelized digital bit streams are routed by variousswitching circuits 622 interconnected by backplane bus 620/624. As shownin FIG. 6, a UNILINK-type data bus couples the various switch ASICs 622in a series of cascading logical rings, with data transfers occurring ina linear fashion via switch interconnections 624 and return bus 620. Inalternate embodiments, the various switch ASICs 622 may beinterconnected in any mesh, web, star, linear, ring or other manner.Switched frequency slices 310 are then recombined at ASICs 610 and/ordigitally processed by regeneration ASICs 616 as appropriate. Therecombined signals may then be D/A converted 612 and provided to thedownlink antennas via output ports 614 as appropriate.

Using the structures and logical constructs shown in FIGS. 2-6, digitalpayloads of varying capabilities may be readily fashioned. Referringagain to FIG. 2, one embodiment of digital payload 200 provides routingand data reconstruction functionality, as well as optionally adjustingoutput power, providing for output linearization, adjusting output powerand/or monitoring traffic and/or bandwidth utilization within payload200. Output linearization, for example, may be provided bypre-compensating data provided to the downlink beams for distortionobserved during the downlink transmission. This pre-compensation may beprogrammably modified on-orbit in response to actual distortionobserved, ground weather conditions, and/or other factors. Similarly,output power of the various downlink beams can be programmably adjustedupwardly or downwardly as needed to compensate for weather changes,evolving technologies, or other factors.

With reference now to FIG. 7, a further embodiment 700 of digitalpayload 200 suitably provides enhanced modular data handling capabilityas appropriate. Such data handling capabilities are typically processedor controlled by regeneration module 308 (FIG. 3) and/or T&C processor520 (FIG. 5). Because the various digital frequency slices 310 (FIG. 3)can be demodulated to extract a raw bit stream, digital payload 200 hasaccess to the channelized signals, thereby allowing the signals to beprocessed and manipulated to implement additional features not readilyavailable in the satellite environment. Examples of data handlingcapabilities include packet switching with additional queuing, forwarderror correction (e.g. using checksum, CRC, digest or other errorcorrection techniques), code based multiplexing (e.g. code divisionmultiple access (CDMA)), and/or enhanced security through userauthentication, access authorization, data encryption and/or the like.Examples of enhanced security include network registration and/or accesscontrol using digital credentials (e.g. passwords, digital signatures orthe like).

In an even further embodiment, the digital signal processingcapabilities of payload 200 can be expanded to incorporate direct beamforming, essentially creating an all-digital satellite payload 800 asshown in FIG. 8. Such embodiments typically do not require downconvertor output multiplexing capabilities, since the digital payload 200 isable to directly interoperate with phased array and/or other antennas toprocess uplink data and to form downlink beams ready for transmission.In such embodiments, digital payload 200 receives the analog basebandsignals from the input amplifiers 206, and provides output signals tooutput amplifiers 802 in analog form. Output amplifiers may be solidstate power amplifiers (SSPAs) or any other suitable amplifiers. Becauseall of the data processing is handled digitally within payload 800,significantly enhanced capabilities such as direct point-to-pointrouting, transmit power and coverage optimization, anti-jammingfunctionality (e.g. nulling) and the like.

Nulling, for example, typically involves detecting a hostile signal atthe antenna and instantly countering with a “null” signal to minimizethe energy of the hostile signal as compared to friendly signals.Because digital payload 200 is able to form individual downlink beamsand to adjust the power of the output beams, nulling functionality canbe directly implemented within payload 200 by creating a desireddownlink signal that can be directed at the hostile source. Moreover,hostile signals can be digitally extracted from uplink signals received,and/or access restrictions can be used to further secure datatransmissions within payload 200.

The architecture described above provides a platform for designing,building and operating satellites and to tailor the performance of suchsatellites to specific applications desired. Both beam coverage andfrequency, for example, can be made variable and changed on-orbit.Moreover, both channelized and regenerative functionalities are madeavailable, and these functionalities can be enhanced or changed whilethe satellite is in orbit. Still further, the flexibility designed intothe system allows a high degree of frequency reuse while maintainingfull communications flexibility.

Because various payload resources (bandwidth, power, etc.) can bereadily monitored and adjusted on-orbit in real time within digitalpayload 200, for example, new techniques for exploiting the payloadresources are enabled. As mentioned above, bandwidth and other resourcesmay be monitored (e.g. by telemetry and command module 520 in FIG. 5 orthe like) to re-assign excess resources to other beams, channels orslices having a need for such resources.

With reference now to FIG. 9, an exemplary process 900 for re-allocatingresources within the payload 200 suitably includes the broad steps ofdefining an initial allocation (step 902), monitoring resource usage(step 904), and adjusting resource allocation upwardly (steps 906 and908) or downwardly (steps 910) as needed. While FIG. 9 refers tobandwidth as the particular resource being allocated, various equivalentembodiments will allocate other resources such as electrical power,antenna coverage and the like.

Process 900 begins with an initial allocation of satellite resources(step 902). The initial allocation may be based upon historical orsimulation data, previous iterations of process 900, experimental dataand/or any other factors. Resource usage is then monitored (step 904)across the various links, channels, slices or other relevant resourcesto identify excess capacity (step 910) or over-utilized capacity (step906). In the case of bandwidth, for example, some or all of the channelscan be monitored to identify particular channels with bandwidthutilizations above or below certain threshold values. The particularthreshold values used may be determined experimentally or fromhistorical data, or may be otherwise determined in any manner.Alternatively, the actual or estimated resource utilizations of variouschannels may be maintained in a table or other data structure. Excesscapacity identified in one or more under-utilized channels (step 912)may then be re-assigned for use by over-utilized channels (step 908), asappropriate. Conversely, channels that are neither over norunder-utilized may not be affected (step 914). Process 900 shown in FIG.9 is intended to be primarily conceptual; in practice, any resourcemonitoring and re-allocation process could be used in a wide array ofalternate embodiments.

The concept of on-orbit resource re-allocation enables various newbusiness methods for bandwidth-provider organizations. Customers can beoffered variable bandwidth services, for example, that are more uniquelytailored to the customer's actual needs than the “transponder circuit”purchase model. Customers may be flexibly charged for actualbandwidth/transmit power consumed and geographical area covered, forexample, rather than paying for an inflexible “pipe” of fixed size andpower that may be over and/or under-utilized by the customer atdifferent times during the contract period. Alternatively, the “excess”or unused bandwidth and transmit power allocated to various circuitconnections may be reclaimed and used for other applications orcustomers.

Another process 1000 enabled by the flexible satellite architecture isshown in the data flow diagram of FIG. 10. Process 1000 allows variousparties to independently control a portion of the satellite resources tothereby allocate the resources as desired. With reference now to FIG.10, a block of satellite resources 1002 is divided and assigned amongstone or more resource managers 1006A-C who are responsible forsub-assigning the resource to various entities 1008A-C operating withinthe manager's domain. Although not shown in FIG. 10, the sub-entitiesmay further sub-assign the resource to still other entities (or multiplesub-levels of entities) in alternate embodiments. Managers 1006 may bebattlefield commanders, for example, who assign satellite bandwidthdynamically among units within their control. If a unit is assigned afixed amount of bandwidth, for example, a commander may temporarilyassign a large portion of bandwidth to one unit (e.g. an unmanned aerialvehicle with a camera) for a short period of time to allow transmissionof visual images, large data files or the like. After the need for thebandwidth subsides, that bandwidth may be re-allocated to other unitsfor enhanced voice, data or other traffic. Such flexibility may beparticularly useful for network centric operations (NCO) and othermilitary purposes, although the general concept could be used incorporate, industrial, entertainment or other governmental settings aswell. Access control could be enforced within digital payload 200 (FIGS.2-8) by assigning digital credentials (e.g. cryptographic certificatesor the like) to the various managers 1006 and other entities 1008 andassociating the various certificates with an access table or other datastructure within payload 202 (e.g. within T&C module 520 or the like).Numerous other allocation plans and techniques could be formulated in awide array of equivalent embodiments.

In various further embodiments (and with reference now to FIG. 11),digital payload 200 can be combined with multi-beam phased array orsimilar antennas capable of projecting multiple spot beams to furtherenhance the flexibility of satellite 1100. In such embodiments,sub-frequency bands can be re-used on the multiple downlink spot beams1106, thereby improving bandwidth efficiency. One or more broadcastbeams 1104 may also be provided. These spot beams may be narrowlytailored and focused to provide bandwidth solely in desired areas, andmay also facilitate frequency hopping techniques that further enhancesecurity.

Accordingly, the overall efficiency of the satellite can be dramaticallyimproved as the entire bandwidth (or other resources) of the satellitebecome available for use at all times during satellite operation. Thiseffectively provides additional resource capacity that can be sold orleased, thereby significantly increasing the revenue streams availablefrom the digital payload. Moreover, the additional digital processingfeatures (e.g. security, data regeneration, code multiplexing and thelike) further improve the usefulness and value of the satellite. Stillfurther, the ability to re-configure the digital payload during design,manufacturing and/or on orbit provides even more value to customers byreducing the long-term risk of investment in such technologies. Becausethe satellite can be reconfigured on orbit to transmit, receive andprocess beams at any frequency and carrying any type of data waveforms,the architecture allows for a wide array of applications and a muchlonger product life than was previously available.

While at least one exemplary embodiment has been presented in theforegoing detailed description, it should be appreciated that a vastnumber of variations exist. Although various aspects of the inventionare frequently described in conjunction with a communications satellite,for example, the various techniques and systems described herein couldbe readily implemented in other contexts, including aviation, automotiveor maritime communications, cellular or other types of terrestrialcommunications, or in any other environment. It should also beappreciated that the exemplary embodiment or exemplary embodiments areonly examples, and are not intended to limit the scope, applicability,or configuration of the invention in any way. The foregoing detaileddescription will provide those skilled in the art with a convenient roadmap for implementing the exemplary embodiment or exemplary embodiments.Various changes can be made in the function and arrangement of elementswithout departing from the scope of the invention as set forth in theappended claims and their legal equivalents. The various steps of themethods, processes and techniques described in the appended claims couldbe practiced in any temporal order, for example, or may be practicedsimultaneously in various equivalent embodiments.

1. A digital payload for processing a sub-band spectrum received on anuplink beam at a communications satellite, the digital payloadcomprising: a digital channelizer configured to divide the sub-bandspectrum into a plurality of frequency slices; a digital switch matrixconfigured to route each of the plurality of frequency slices to atleast one of a plurality of receiving ports; a digital combinerconfigured to communicate with the receiving ports to receive theplurality of frequency slices and to re-assemble the plurality offrequency slices to thereby form a plurality of output sub-bands fortransmission on an output beam of the communications satellite; and adigital regeneration module configured to demodulate each of theplurality of frequency slices to extract a digital bitstream therefrom,to digitally process the bitstream, and to remodulate the bitstreamafter processing, wherein the digital regeneration module is furtherconfigured to digitally process the bitstream by performingcryptographic manipulation of the bitstream.
 2. The digital payload ofclaim 1 wherein the digital regeneration module is further configured todigitally process the bitstream by performing error correction.
 3. Thedigital payload of claim 1 wherein the digital regeneration module isfurther configured to digitally process the bitstream by performing codedivision multiplexing.
 4. The digital payload of claim 1 wherein thedigital regeneration module is further configured to digitally processthe bitstream by performing access control.
 5. The digital payload ofclaim 1 wherein the digital regeneration module is further configured todigitally process the bitstream by performing network registration. 6.The digital payload of claim 1 further comprising a controllerconfigured to monitor bandwidth consumption of the sub-band spectrum andto adjust the bandwidth consumption in response thereto.
 7. The digitalpayload of claim 1 further comprising a built-in test circuit.
 8. Thedigital payload of claim 1 further comprising an analog to digital (A/D)converter configured to receive the uplink beam and to produce thesub-band spectrum therefrom.
 9. The digital payload of claim 8 whereinthe A/D converter is further configured to sample the uplink beam at anIF frequency rate.
 10. The digital payload of claim 1 further comprisinga digital-to-analog (D/A) converter.
 11. The digital payload of claim 10wherein the D/A converter is further configured to operate at an RFfrequency rate.
 12. An all-digital payload for processing a plurality ofsub-band spectra received on a plurality of uplink beams at acommunications satellite, the digital payload comprising: a digitalchannelizer configured to divide each of the sub-band spectra into aplurality of data packets the sub-band spectra being in an intermediatefrequency (IF); a digital switch matrix configured to route each of theplurality of data packets to at least one of a plurality of receivingports; an embeddable digital regeneration module in communication withthe digital switch matrix, wherein the digital regeneration module isconfigured to demodulate at least a portion of the plurality of datapackets to extract a digital bitstream therefrom, to digitally processthe bitstream, and to remodulate the bitstream after processing, whereinthe embeddable regeneration module is further configured to digitallyprocess the bitstream by performing cryptographic manipulation of thebitstream; and a digital combiner configured to communicate with thereceiving ports to receive the plurality of data packets and tore-assemble the plurality of data packets to thereby form a plurality ofoutput sub-bands for transmission on an output beam of thecommunications satellite.
 13. A method of processing a sub-band spectrumreceived on an uplink beam at a digital payload for a communicationssatellite, the method comprising the steps of: digitally dividing thesub-band spectrum into a plurality of frequency slices; routing each ofthe plurality of frequency slices to at least one of a plurality ofreceiving ports; demodulating at least a portion of the plurality offrequency slices to extract a digital bitstream therefrom; digitallyprocessing the bitstream by performing cryptographic manipulation of thebitstream; remodulating the bitstream after processing; and digitallyre-assembling the portion of the plurality of frequency slices afterprocessing to thereby form a plurality of output sub-bands fortransmission on an output beam of the communications satellite.
 14. Themethod of claim 13 further comprising the steps of converting the analoguplink beam to a digital representation of the sub-band spectrum priorto the dividing step.
 15. The method of claim 14 wherein the convertingstep occurs at an IF frequency rate.
 16. The method of claim 13 whereinthe routing step comprises simultaneously routing at least a portion ofthe plurality of frequency slices to multiple receiving ports to therebyimplement a multi-cast function.
 17. The method of claim 13 furthercomprising the steps of monitoring the sub-band spectrum to identifychanges in bandwidth consumption and adjusting the routing step inresponse to the changes to thereby improve the efficiency of the digitalpayload.
 18. A satellite receiving a plurality of uplink beams andproducing a plurality of downlink beams, the satellite comprising: anuplink antenna configured to receive the plurality of uplink beams; adownlink antenna configured to produce the plurality of downlink beams;an analog-to-digital (A/D) converter configured to convert the uplinkbeams to digital uplink equivalents; an all-digital payload comprising:a digital channelizer configured to receive the digital uplinkequivalents and to divide the digital uplink equivalents into aplurality of frequency slices; a digital switch matrix configured toroute each of the plurality of frequency slices to at least one of aplurality of receiving ports; and a digital combiner configured tocommunicate with the receiving ports to receive the plurality offrequency slices and to re-assemble the plurality of frequency slices tothereby form a plurality of digital output sub-bands; a digital toanalog (D/A) converter configured to convert the digital outputsub-bands to downlink beams transmitted by the downlink antenna; and adigital regeneration module configured to demodulate each of theplurality of frequency slices to extract a digital bitstream therefrom,to digitally process the bitstream, and to remodulate the bitstreamafter processing, wherein the digital regeneration module is furtherconfigured to digitally process the bitstream by performingcryptographic manipulation of the bitstream.
 19. The satellite of claim18 wherein the A/D converter is further configured to sample the uplinkbeams at an IF frequency.
 20. The satellite of claim 18 wherein the D/Aconverter is further configured to sample the output sub-bands at an RFfrequency.
 21. The satellite of claim 18 wherein the uplink antenna is adigital beam-forming antenna.
 22. The satellite of claim 18 wherein theuplink antenna is a phased array antenna.
 23. The satellite of claim 18wherein the downlink antenna is a digital beam-forming antenna.
 24. Thesatellite of claim 18 wherein the downlink antenna is a phased arrayantenna.
 25. A digital payload for a satellite configured to receive aplurality of sub-band spectrum via an uplink beam and to provide adownlink beam, the digital payload comprising: a backplane housinghaving a backplane bus; and a plurality of processing cards, eachprocessing card comprising: a channelizer circuit configured to receiveat least one of plurality of sub-band spectra and to divide the at leastone of the plurality of sub-band spectra into a plurality of frequencyslices; a digital switch matrix comprising a plurality of switchingcircuits, wherein each of the plurality of switching circuits isconfigured to route a portion of the plurality of frequency slices to atleast one of a plurality of receiving ports via the backplane bus; and adigital combiner circuit configured to communicate with the receivingports to receive the plurality of frequency slices and to re-assemblethe plurality of frequency slices to thereby form an output sub-band fortransmission on the output beam.
 26. The digital payload of claim 25wherein each of the plurality of processing cards further comprises aregeneration circuit configured to demodulate at least a portion of theat least one of the plurality of sub-band spectra to thereby extract adigital bitstream therefrom, to digitally process the bitstream, and toremodulate the bitstream after processing.
 27. Means for processing asub-band spectrum received on an uplink beam at a communicationssatellite, the means for processing comprising: means for dividing thesub-band spectrum into a plurality of frequency slices; means forrouting each of the plurality of frequency slices to at least one of aplurality of receiving ports; means for demodulating at least a portionof the plurality of frequency slices to extract a digital bitstreamtherefrom; means for digitally processing the bitstream by performingcryptographic manipulation of the bitstream; means for remodulating thebitstream after processing; and means for communicating with thereceiving ports to receive the plurality of frequency slices and tore-assemble the plurality of frequency slices to thereby form aplurality of output sub-bands for transmission on an output beam of thecommunications satellite.
 28. The means for processing of claim 27further comprising a means for digitally regenerating the sub-bandspectrum, wherein the means for digitally regenerating comprises meansfor demodulating at least a portion of the sub-band spectrum to extracta digital bitstream therefrom, means for digitally processing thebitstream, and means for remodulating the bitstream after processing.